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Pneumococcal polysaccharide serotype 5 conjugated to CRM197 is a vaccine component that protects against disease caused by Streptococcus pneumoniae serotype 5, a bacterial strain that can cause pneumonia, meningitis, and bloodstream infections. The full registry name lists it among many polysaccharide serotypes conjugated to CRM197, a carrier protein derived from diphtheria toxoid.[1] The substance is part of authorised pneumococcal conjugate vaccines including Vaxneuvance (15-valent) and Prevnar 20 (20-valent), which are marketed by Sanofi Pasteur Inc. and Merck Sharp & Dohme B.V.[1][2] It is also a component of the investigational 21-valent pneumococcal conjugate vaccine (PCV21) being studied in infants.[1]
Conjugation links the pneumococcal polysaccharide (a sugar coating from the bacterium) to the CRM197 carrier protein. This protein carrier helps the infant immune system recognise the polysaccharide as a threat and produce protective antibodies, specifically immunoglobulin type G (IgG).[4] When the immune system later encounters real Streptococcus pneumoniae serotype 5, these antibodies can help prevent infection. The conjugate approach is particularly important for young children, whose immune systems respond poorly to polysaccharides alone.[4]
The substance is given as a suspension for injection by intramuscular injection, typically in a 0.5 ml dose.[1] In authorised vaccines such as Synflorix, which uses a different carrier protein, serotype 5 polysaccharide is present at 1 microgram per 0.5 ml dose.[3] The product comes in pre-filled syringes or vials, and a paediatric formulation exists for use in infants.[1]
One Phase 3 trial in the EU Clinical Trials Information System is investigating a 21-valent pneumococcal conjugate vaccine (PCV21) that includes serotype 5 conjugated to CRM197.[1] The trial enrols 1,113 healthy infants from approximately 2 months of age and compares PCV21 against the authorised 15-valent vaccine Vaxneuvance (15vPCV).[1] The primary outcomes are the seroresponse rate (the proportion of infants who produce a defined antibody response) and IgG concentrations measured 30 days after the toddler dose.[1] For shared serotypes, including serotype 5, the trial aims to show PCV21 is non-inferior to 15vPCV; for six serotypes unique to PCV21, it aims to show superiority.[1] The trial is currently authorised, meaning it has regulatory approval to proceed.[1]
No side effect data specific to this substance alone was provided in the supplementary sources. Side effects of pneumococcal conjugate vaccines are typically assessed in the clinical trials themselves and reported in product information for the authorised vaccines.
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